Chapter 27. XQuery for XSLT Users

XQuery and XSLT have a lot in common: a data model, a set of built-in functions and operators, and the use of path expressions. This chapter delves further into the details of the similarities and differences between XQuery and XSLT. It also alerts XSLT 1.0/XPath 1.0 users to differences and potential compatibility issues when moving to XQuery.

XQuery and XPath

XPath started out as a language for selecting elements and attributes from an XML document while traversing its hierarchy and filtering out unwanted content. XPath 1.0 is a fairly simple yet useful recommendation that specifies path expressions and a limited set of functions. XPath has since become much more than that, encompassing a wide variety of expressions and functions, not just path expressions.

XQuery and XPath overlap to a very large degree. They have the same data model and the same set of built-in functions and operators. XPath is essentially a subset of XQuery. XQuery has a number of features that are not included in XPath, such as FLWORs and XML constructors. This is because these features are not relevant to selecting, but instead have to do with structuring or sorting query results. The two languages are consistent in that any expression that is valid in both languages evaluates to the same value by using both languages.

XQuery Versus XSLT

XQuery and XSLT are both languages designed to query and manipulate XML documents. There is an enormous amount of overlap among the features ...

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